In prior techniques for measuring the liquid level in a large tank, generally a measuring rod was lowered into the tank by an attendant, especially in the case of subterranean tanks at fuel depots and the like, or some float-type of system was used to detect the position of a float line on the liquid surface. For very large tanks, the attendant was required to clamber down through the opening, such as a manhole, to measure the liquid level in some mechanical manner.